Cross-linking of polymeric epoxides



Unite States Patent 3,026,270 CRBSS-LINKING F POLYMERIC EPOXlDESAnderson E. Robinson, Jr., Newark, Del., assignor to Hercules PowderCompany, Wilmington, Del., a corporation of Delaware No Drawing. FiledMay 29, 1958, Bar. No. 738,629 20 Claims. (Cl. 260-2} This inventionrelates to unique special purpose rubbers and more particularly to thevulcanizates produced by cross-linking poly epihalohydrin) s.

For many rubber applications specialty rubbers are required and no onerubber has previously been known that had the requisite physicalproperties that it could be substituted for these many specialtyrubbers. For example, if it had solvent resistance, it lacked high orlow temperature resistance, etc.

Now, in accordance with this invention, it has been found that highmolecular weight polymers and copolymers of epihalohydrins may bevulcanized, i.e.- crosslinked, with polyamines to produce a rubber thathas the good attributes of a number of the so-called specialty rubbersand hence, may be used as what might be termed, a general purposespecialty rubber. They have excellent resistance to all classes ofsolvents, polar and nonpolar, aliphatic and aromatic, excellent agingcharacteristics, excellent high and low temperature performance andexcellent general elastomeric quality. Hence, these new rubbers may beused in place of the several difierent specialty rubbers now on themarket.

.Any high molecular weight polymer, homopolymer or copolymer, of anepihalohydrin, as for example, epichlorohydrirl or epibromohydrin,homopolymers or copolymers with one or more other epoxides may becross-linked with a polyamine to produce the valuable new vulcanizatesof this invention. These polymers are readily prepared by polymerizationof epihalohydrins with, for example, organoaluminurn compounds ascatalysts. Particularly effective catalysts for the polymerization of,epihalonydrins are alkylaluminum compounds that have been reacted withfrom about 0.2 to about 1 mole of water per mole of alkylaluminumcompound. The polymer obtained by means of these catalysts may beessentially wholly amorphous or crystalline or it may be a mixture ofthe amorphous and crystalline polymers. Generally, the amorphouspolymers are preferred since the crystalline polymers on vulcanizationtend to be hard, brittle and lacking in elasticity. These propertiesare, of course, useful in the case of molded articles which may beprepared by molding the compounded polymer and then curing to cross-linkand set it. However, excellent rubber-like materials are obtained byvulcanizing mixtures of amorphous and crystal line polymers. in thiscase, the amount of the crystalline polymer is generally less than about25 to 30% of the mixture. When epihalohydrins are polymerized by thisprocess, polymerization takes place, at least in major part, through theepoxide linkage so that the product is a polyether containing halomethylgroups attached to the main polymer chain. They are believed to have thefollowing general formula where X is halogen. In the same way, when anepihalohydrin is copolymerized with one or more other epoxides,polymerization takes place through the epoxide linkage even thoughethylenic unsaturation or other polymerizable groups may be present.Typical of epoxides that may be copolymerized with an epihalohydrin toproduce a copolymer that may be cross-linked in accordance with thisinvention are the alkylene epoxides such as ethylene oxide,

propylene oxide, butene oxides, etc., butadiene monoxide, cyclohexeneoxide, vinyl cyclohexene oxide, epoxy others such as ethyl glycidylether, 2-chloroethyl glycidyl ether, hexyl glycidyl ether, allylglycidyl ether, etc.

As pointed out above, the poly(epihalohydrin)s that are vulcanized orcross-linked in accordance with this invention are high molecular Weightpolymers. Any homopolymer or copolymer that has a reduced specificviscosity of at least about 0.2, as measured on an 0.1% solution inu-chloronaphthalene at C., may be cross-linked with a polyamine to yielda polymer of increased tensile strength and modulus. The term ReducedSpecific Viscosity (RSV), which is a function of molecular Weight isused herein to designate the specific viscosity measured at 100 C. on ana-chloronaphthalene solution of the polymer, containing 0.1 gram per 100ml. of solution, corrected to zero shear gradient, divided by theconcentration of the solution. :Polymers having an RSV of from about 0.2to about 0.5 may be cross-linked as described herein to yieldvulcanizates of increased tensile strength and modulus and while thesevulcanizates are generally not useful as specialty rubbers, they areuseful as potting compounds. However, polymers having an RSV of about0.5 and above on cross-linking yield excellent rubbery polymers that, aspointed out above, they may be used as general purpose specialtyrubbers.

These poly(epihalohydrin)s and epihalohydrin copolymers are cross-linkedby heating a mixture of the polymer and a polyamine to an elevatedtemperature for a short time. Any amine containing two or more aminogroups may be used as the cross-linking agent in accordance with thisinvention. The amino groups may be primary, secondary or tertiary aminogroups. Exemplary of such polyar'nines are hydrazine, aliphatic aminessuch as ethylenediamine, propylenediamine, tetramethylenediamine,hexamethylenediamine,etc.,up to alkylenediamines of 20 carbon atoms ormore, diethylenetriamine, etc., cycloaliphatic amines such as melamine,piperazine, pyrazine (paradiazine), etc., aromatic amines such asp-phenylenediamine, naphthalenediarnine, biphenyldiamine, etc. andpolymeric amines such as poly(2-methyl-5-vinylpyridine), etc. Instead ofthe free amine, a salt of the amine may be used as, for example, thehydrogen halides, in which case an alkaline material such as calcium orbarium oxide is also added. Internal salts of the amines may also beused, as for example, hexamethylenediamine carbamate, which type of saltdecomposes to the free amine at or below the curing temperature.

The polyamine may be incorporated or admixed with the polym'er'in anydesired fashion. For example, the amine and polymer may be uniformlyblended by simple milling on a conventional rubber mill. By this meansthe amine is uniformly distributed throughout the polymer and uniformcross-linking is eifected when the blend is subjected to heat. When theamine is blended with the polymer, cold roll milling procedures may beused, as for example, with the rolls cooled to about 50 F. or themilling may be done at room temperature or above, in the latter casewith one roll preferably slightly warmer than the other. Other methodsof admixing the amine with the polymer will be apparent to those skilledin the art. Any amount of the polyamine may be added and will dependchiefly upon the degree of cross-linking desired. Generally, from about0.5% to about 10% and preferably from about 1% to about 5% of the aminebased on the Weight of the polymer will be added.

The temperature at which the cross-linking is effected may be variedover a wide range. It may be effected in minutes at temperatures around300 F. or in days at room temperature. To some extent, it depends uponthe type of amine being used as the cross-linking agent. For example,with a compound such as hexamethylenediamine carbamate, an inner saltwhich is stable at processing temperatures up to 175 F., but whichreleases its free amine at higher temperatures, requires the highervulcanization Preparation of Vulcanizate and Properties Polymercompositons were made up by mixing on a two-roll mill (rolls cooled toabout 50 F.) 100 parts of 9 In general the cross'linkingo temperaturethe polymer and the specified polyamine and any other 32 6 2 52 3 2;igii gf igg ig g 2 2533:; 5 additives as shown in Table I for each examplefor about p y 5 minutes. The stocks Were then cross-linked by heatingand W111 vary mversia'ly Wlth the temperature of from at 300 F. for 40minutes. The extent of cross-liking: 2 3 2 5; 12 :3 g g gi i Preferablyfrom about was determined by analysis for percent gain in inso1u-- Ibility in solvents in which uncross-linked polymer is solu-- v n additon to the amine, other mgredients may also be b1 6 This is termadpercent gel hereinafter Data incorporated. The additives commonly usedin rubber V I vulcanization may be used here also as, for example, exi gi i 3 I ggg blank formug fiHerSdp-igment lilasticizgrs gi g i a The percerit gei E perc:nY s vve l l are determined as o a er, an 111 partlcuar car on ac 1s ene c1a and, as in rubber compounding gives optimumresults. 5 2 {1 g g g zg gi gi ggggfi g gg gg gg cbvl-ously film-e ammany casas m whlch a finer Is not closed container for 48 hours. Thesample is then reig g or d-eslred g Excellent results are achieved whenmoved blotted on filter paper without squeezing so as to o t e amine a gfollowings exaniples will illustrate the process of remove toluene onthe surface and welghed at once. The gins-lin n epihgilothydrinpolymflrs in accordance with zggggg sg g 2%;21331 g f g ig isg g z g i?s invention an t 'ei All Parts and g i z g g fi so Obtained The weightsof initial and final sample are corrected for nonpolymer content basedon knowledge of components. EXAMPLES From these figures: These examplesdemonstrate the use of various poly- C t d d i ht amines forcross-linking poly(epichlorohydrin). m 100=Perce11t gel P reparationPoly(el7ichlor0hydrin) Similarly percent swell is calculated by theformula: A polymerization vessel with a nitrogen atmosphere was Swollenweighgcorrected d weight charged with diethyl ether and 10 parts ofepichloro- Corrected dry Weight hydrin. After equilibrating at 30 C., asolution of the X lo() t u catalyst was injected. The catalyst solutionwas pre- TPBrGeD SW6 TABLE I Example Blank 1 2 3 4 5 6 7 8 9 10 11 12 1314 e 1e t i ii on (pm 5) 100 100 100 100 100 100 100 100 100 100 100 100100 100 100 Melamine... HMDA-C 1 2. 5 5 TMDA-2HC1 2 4 EDA- 1 2Hydrazine-2HO1 l. 5 3 FDA! 1.5 3 Piperazine. 5 51 d i) 6 n 1 5 3 1 5 3 u10 Perden t G61 Formation--- 0 "2? 59 100' 105 '68 61 "130' "51? a. 42101 105 102 82 Percent Swell (toluene)... in 335 416 284 101 41s 398 391310 424 384 223 152 270 1,005

1 Hexarnethylenediarnine carbamate. 2 Tetramethylenediaminedihydroehloride. 3 Ethylenediamine. 4 p-Phenylenediamine. 5 Poly(2-methyl-5-vinylpyridine). 6 Magnesium oxide.

pared1 by diluting a molar solution of triisobutylaluminum EXAMPLES15-23 in neptane to 0.5 molar with ether adding an amount These examplesdemonstrate the cross-linking with hexf gfg ig g gggg gg gigfi g gg ifH101: 233 3 amethylenediamine carbamate of epichlorohydrin poly- Anamount o f this catal st soluti ri e 111352 11? t 079 mas of VaryingRSVS compounded with carbon black Part of tril-sobut laluminusrln wasused s the O1 0 and/or neutral silica and the physical properties of thetion The totalydflu nt re m (muted t P g s vulcanizates so obtained. Theamounts of the ingredients and'contained 84% 5; 1 p 19 used in eachexample are tabulated in Table H along with hours 1 C the polymerizationwas Stopped by adding the physical properties of each. The cross-linkingwas 4 parts of anhydrous ethanol. The mixture was then i f g outlm 32 13 for h at 38 except diluted with 40 parts of ether, after which theethero Xamp e W c was eate minutes at insoluble polymer was collectedand washed twice with 300 ether. It was purified by slurrying theinsoluble polymer The polfleplchlofohydfm) used 111 Examples and with a1% solution of hydrogen chloride in ethanol. It 2 ad an RSV of 0.75 andWas prepared essentially as was again collected, washed with methanoluntil neutral, 1H E p abOVe- The P Y( P then with an 0.4% solution ofSantonox, i.e., 4,4-thiobishydrm) used in Example 19 had an RSV of 3.4again by (6-tert-butyl-m-crcsol), in methanol and finally was dried.essentially the same procedure except that in this case the Thepoly(epichlorohydrin) so prepared had an RSV of triisobutylaluminum wasnot prereacted with water. The 1.2. It was largely amorphous, containingless than about polymers used in Examples 20 and 21 were prepared by 10%crystalline polymer. 7 the same procedure described in Examples 1 14except By the term RSV is meant Reduced Specific Viscosity that thediluent was n-heptane and the polymenzauon was which is the C determinedon a 0.1% solution of the carried out at 30 and 65 C., respectively. Thepolymer of Example 23 was again prepared by the procedure used polymerin a-chloronaphthalene at C.

. 3 for Examples 1-14 except that the catalyst was triethylaluminum thathad been prereacted with 0.6 mole of water per mole of aluminum. Thispolymer was essentially all amorphous polymer.

'5 part of triisobutylaluminum in n-heptane which had been reacted with0.5 mole of acetylacetone per mole of aluminum and then with 0.5 mole ofwater per mole of aluminum, was added. After 6 hours at 30 C. the poly-TABLE II Example 16 17 18 19 20 21 22 23 RSV 0. 75 0. 75 0.75 0. 75 3. 40. 57 0.27 0. 75 2. 8 Composition:

Polymer 100 100 100 100 100 100 100 100 100 Carbon Black 0. 25 12. 5 50Carbon Black A 25 12. 5 12. 5 12. 5 12. 5 50 Neutral Silica. 12. 5 12. 512. 5

3 3 3 3 5 3 3 4 1. 25 565 l, 075 1, 655 l, 390 400 450 90 2,000 280 400395 1, 200 215 155 65 560 odulus, p s 1 555 250 1,350 300% Modulus,p.s.i 930 1, 900 400% Modulus, p.s.i 1, 510 Ultimate Elongation, percent315 240 295 420 110 190 245 150 71 Shore Hardness A2 63 60 38 31 25 Thehigh modulus poly(epichlorohydrin) vulcanizate of Example 19, the lowmodulus poly(epichlorohydrin) vulcanizate of Example 18, and the gumvulcanizate of poly(epichlorohydrin) of Example 22 were tested forsolubility in a number of solvents. The volume percent swell istabulated below.

Volume Percent Swell The vulcanizate of Example 18 was tested for itsstability to light and weather. It was unchanged after three monthsoutdoor exposure and in accelerated aging tests was still unchangedafter 2500 hours in both the Fade- Orneter and the Weather-Ometer.

EXAMPLE 24 Epibromohydn'n was polymerized by the same general proceduredescribed above for epichlorohydrin using as catalysttriisobutylaluminum that had been prereacted with 0.5 mole of water permole of aluminum compound. The ether-insoluble polymer that had formedafter 19 hours at C. was separated and then extracted with acetone atroom temperature. The acetone-soluble polymer was recovered by removingthe acetone and treating the residue with methanol containing 0.2%Santonox and finally drying at 80 C. under vacuum. Thepoly(epibromohydrin) so obtained was a tough, rubberymaterial having anRSV of 0.8 and a bromine analysis in agreement with the theoreticalvalue. It was shown to be amorphous by X-ray.

This poly(epibromohydrin) was cross-linked by milling together 100 partsof the polymer, 12.5 parts carbon black, 12.5 parts silica and 4 partsof hexamethylenediamine carbamate and then heating the mixture for 40minutes at 300 F. The vulcaniza-te so obtained was insoluble incyclohexanone after 4 hours at 60 C. and had properties typical of across-linked elastomer.

EXAMPLE 25 A polymerization vessel with a nitrogen atmosphere wascharged with 35 parts of n-heptane, 2 parts of epichlor'ohydrin and 8parts of propylene oxide. After equilibrating at 30 C., a catalystsolution consisting of 0.79

merization was stopped by adding 4 parts of anhydrous ethanol and thereaction mixture was diluted with an equal volume of diethyl ether. Thereaction mixture was then washed with a 3% aqueous hydrogen chloridesolution, with water until neutral, with a 2% aqueous sodium.bicarbonate solution and again with water. After adding Santono'x'equalto 0.5% based on the polymer, the ethern-heptane diluent was removed andthe polymer was dried. The epichlorohydrin-propylene oxide copolymer soob tained was a tacky, snappy rubber that had an RSV of 5.7 (0.1%solution in benzene at 25 C.) and was soluble in benzene and n-heptane.A chlorine analysis showed that it contained 12% of the epichlorohydrinmonomer.

This epichlorohydrin-propylene oxide copolymer was cross-linked bymilling together parts of the copolymer with 2 parts of ethylenediamineand then heating at 300 F. for 40 minutes. The vulcanizate so obtainedhad a percent gel formation of 82 and percent swell of 1425 incomparison to O and 00, respectively, for the control where no amine wasadded.

What I claim and desire to protect by Letters Patent is:

1. A cross-linked polymer of an epihalohydrin which has been prepared byheating a polymer of an epihalohydrin at a temperature of from about 250F. to about 340 F. for a period of from about 60 minutes to about 5minutes with from about 0.5% to about 10% of one of the group consistingof polyamines, hydrogen halide salts of polyamines, and polyaminecarbamates, said polymer of an epihalohydrin being predominatelyamorphous, having a crystalline polymer content of less than about 30%,having a reduced specific viscosity of at least 0.2 as measured at 100C. on a 0.1% solution in cc-ChOIO- naphthalene, and selected from thegroup consisting of poly(epihalohydrin)s and copolymers of anepihalohydrin with at least one other vicinal monoepoxide, the repeatingepihalohydrin units in said polymer being of the formula where X ishalogen and being joined to any other copolymerized vicinal monoepoxidethrough the oxygen of the epoxide ring of said vicinal monoepoxide.

2. The product of claim 1 wherein the epihalohydrin polymer ispoly(epihalohydrin).

3. The product of claim 1 wherein the epihalohydrin polymer is acopolymer of an epihalohydrin and at least one other vicinalmonoepoxide.

4. The product of claim 2 wherein the poly(epihalohydrin ispoly(epichlorohydrin).

5. The product of claim 2 wherein the poly(epihalohydrin) ispoly(epibromohyd-n'n) 6. The product of claim 3 wherein the copolymer isa copolymer of epichlorohydrin and propylen oxide.

7. A cross-linked polymer of epichlorohydrin which 7 7 has been preparedby heating, at a temperature of from about 250 F. to about 340 F. for aperiod of about 60 minutes to about minutes, an essentially amorphouspoly(epichlorohydrin) having a reduced specific viscosity of at least0.5 as measured at 100 C. on a 0.1% solution in u-chloronaphthalene, therepeating epichlorohydrin units in said polymer being of the formula([3H-CB1-O omol with from about 0.5% to about of an amine containing atleast two primary amino groups.

8. A cross-linked polymer of epichlorohydrin which has been prepared byheating, at a temperature of from about 250 F. to about 340 F. for aperiod of about 60 minutes to about 5 minutes, an essentially amorphouspoly(epichlorohydrin) having a reduced specific Viscosity of at least0.5 as measured at 100 C. on a 0.1% solution in a-chloronaphthalene, therepeating epichlorohydrin units in said polymer being of the formula lCHzCl and being joined to the copolymerized propylene oxide unitsthrough the oxygen of the epoxide ring of said propylene oxide, withfrom about 0.5% to about 10% of an amine having at least two primaryamino groups.

10. A cross-linked polymer of epichlorohydrin which has been prepared byheating, at a temperature of from about 250 F. to about 340 F. for aperiod of about 60 minutes to about 5 minutes, an essentially amorphouspoly(epichlorohydrin) having a reduced specific viscosity of at least0.5 as measured at 100 C. on a 0.1% solution in a-chloronaphthalene, therepeating epichlorohydrin units in said polymer being of the formulawith from about 0.5% to about 10% of ethylenediamine.

11. A cross-linked polymer of epichlorohydrin which has been prepared byheating at a temperature of from about 250 F. to about 340 F. for aperiod of about 60 minutes to about 5 minutes, an essentially amorphouspoly (epichlorohydrin) having a reduced specific viscosity of at least0.5 as measured at 100 C. on a 0.1% solution in u-chloronaphthalene, therepeating epichlorohydrin units in said polymer being of the formulawith from about 0.5% to about 10% of hexamethylenediamine carbamate.

12. A cross-linked polymer of epichlorohydrin which has been prepared byheating, at a temperature of from about 250 F. to about 340 F. for aperiod of from about 60 minutes to about 5 minutes, an essentiallyamorphous copolymer of epichlorohydrin and propylene oxide, having areduced specific viscosity of at least 0.5 as measured at 100 C. on a0.1% solution in a-chloro- 8 naphthalene, the repeating epichlorohydrinunits in said polymer being of the formula OH-CHz-O CHQCI and beingjoined to the copolymerized propylene oxide units through the oxygen ofthe epoxide ring of said propylene oxide, with from about 0.5% to about10% of ethylenediamine.

13. The process of cross-linking a substantially amorphous polymer ofepihalohydrin which comprises heating said polymer, at a temperature offrom about 250 F. to about 340 F. for a period of about 60 minutes toabout 5 minutes, with from about 0.5% to about 10% of one of the groupconsisting of polyamines, hydrogen halide salts of polyamines, andpolyamine carbamates, said polymer of an epihalohydrin having a reducedspecific viscosity of at least about 0.5 as measured at C. on a 0.1%solution in a-chloronaphthalene and which is selected from the groupconsisting of poly(epihalohydrin)s and copolymers of an epihalohydrinwith at least one other vicinal monoepoxide, the repeating epihalohydrinunits in said polymer being of the formula where X is halogen and beingjoined to any other copolymerized vicinal monoepoxide through the oxygenof the epoxide ring of said vicinal monoepoxide.

14. The process of claim 13 wherein the polymer is an essentiallyamorphous poly(epichlorohydrin).

15. The process of claim 13 wherein the polymer is an essentiallyamorphous poly(epibromohydrin) 16. The process of claim 13 wherein thepolymer is an essentially amorphous copolymer of epihalohydrin andpropylene oxide.

17. The process of cross-linking an essentially amorphouspoly(epichlorohydrin) having a reduced specific viscosity of at leastabout 0.5 as measured at 100 C. on a 0.1% solution ina-chloronaphthalene, the repeating epichlorohydrin uni-ts in saidpolymer being of the formula CHOH2O- which comprises heating saidpolymer, at a temperature of from about 250 F. to about 340 F. for aperiod of from about 60 minutes to about 5 minutes, with from about 0.5%to about 10% of an amine containing at least two primary amino groups.

18. The process of cross-linking an essentially amorphous copolymer ofepichlorohydrin and propylene oxide having a reduced specific viscosityof at least about 0.5 as measured at 100 C. on a 0.1% solution inonchloronaphthalene, the repeating epichlorohydrin uni-ts in saidpolymer being of the formula and being joined to the copolymerizedpropylene oxide units through the oxygen of the epoxide ring of saidpropylene oxide, which comprises heating said copolymer, at atemperature of from about 250 F to about 340 F. for a period of fromabout 60 minutes to about 5 minutes, with from about 0.5% to about 10%of an amine containing at least tWo primary amino groups.

19. The process of claim 17 wherein the amine in hexamethylenediaminecarbamate.

20. The process of claim 17 wherein the amine is ethylenediamine.

References Cited in the file of this patent UNITED STATES PATENTS2,451,174 Router Oct. 12, 1948 (Other references on following page) 9 10UNITED STATES PATENTS 2,840,533 Hwa June 24, 1958 2,699,435 Auten et a1.Ian. 11, 1955 gli g 3 2,706,189 Pruitt et a1 Apr. 12,1955 1 w 12,712,000 Zech June 28, 1955 5 OTHER REFERENCES 2,714,276 Landes 1955Narracott: British Plastics, v01. 24, October 1951,

2,694,655 Pullman et a1 Nov, 16, 1956 pp 341 345

1. A CROSS-LINKED POLYMER OF AN EPIHALOHYDRIN WHICH HAS BEEN PREPARED BYHEATING A POLYMER OF AN EPIHALOHYDRIN AT A TEMPERATURE OF FROM ABOUT250*F. TO ABOUT 340*F. FOR A PERIOD OF FORM ABOUT 250*F. TO ABOUT 5MINUTES WITH FROM ABOUT 0.5% TO ABOUT 1/% OF ONE OF THE GROUP CONSISTINGOF POLYAMINES, HYDROGEN HALIDE SALTS OF POLYAMINES, AND POLYAMINES,HYDROGEN HALIDE POLYMER OF AN EPIHALOHYDRIN BEING PREDOMINATELYAMORPHOUS, HAVING A CRYSTALLINE POLYMER CONTENT OF LESS THAN ABOUT 30%,HAVING A REDUCED SPECIFIC VISCOSITY OF AT LEAST 0.2 AS MEASURED AT100*C. ON A 0.1% SOLUTION IN A-CHORONAPHTHALENE, ADN SELECTED FROM THEGROUP CONSISTING OF POLY(EPIHALOHYDRIN)S AND COPOLYMERSOF ANEPIHALOHYDRIN WITH AT LEAST ONE OTHER VICINAL MONOEPOXIDE, THE REPEATINGEPIHALOHYDRIN UNITS IN SAID POLYMER BEING OF THE FORMULA